'How goes the empire?" Perhaps Tony Blair will be tempted to repeat King George V's dying words as he prepares to shuffle off his own political coil. It is a measure of the extent to which the prime minister's foreign policy has restored imperialism to the political vocabulary of the country that, when his legacy is debated, the state of empire will be the main issue.

The answer is that it goes pretty badly. The new imperialism which will for ever be linked to the names Bush and Blair has taken just five years to hit the buffers of popular opposition and moral ignominy. Imperialism has moved from the realm of political jargon to be the central issue of our time - and is seen as such everywhere beyond the ramparts of the neoconservative-New Labour alliance.

In Iraq, the great testing ground for "liberal interventionism", the pitch of resistance to the armies of occupation, along with the failure of a parade of hand-picked premiers to deliver even a facade of stability, is, according to the New York Times, leading George Bush to consider abandoning his "democratic" experiment in favour of, presumably, a dictatorship.

In Afghanistan, to which British troops were rushed nearly five years after regime change was imposed, the Karzai government is floundering in epic levels of corruption. It has reinstated the power of opium-funded warlords, the suppression of whom was perhaps the Taliban's only popular achievement. The consequence has been a conflict of a ferocity that the British army has not seen since the Korean war, according to Lieutenant-General David Richards, the commander on the spot.

And despite Blair's determined green light to Israel's attack on Lebanon, the "long, strong arm of the US" in the region - as the Israeli commentator Sima Kadmon describes his country - has had to retreat with its objectives unmet. No one seems to be rushing to pick up the white man's burden there either.

British troops are now back "east of Suez" with a vengeance. According to the foreign-policy establishment thinktank Chatham House, the big winner from five years of them rampaging around the region is Iran. Presumably that was not the plan. Even in the Balkans, the occupations of Bosnia and Kosovo fester, with the underlying conflicts in no way resolved.

The Blair years have been a study in the failures of the Anglo-Saxon powers' capacity to remake the world in their own interests by force. Even the prime minister seemed to acknowledge that wearily in California earlier this month. Of course, the policy has had its friends. The rightwing historian - and proponent of a genetics of racism - Niall Ferguson has taken the case for empires back on to the television, while the chancellor of the exchequer has insisted it is time Britain stopped apologising for empire. As the South African president, Thabo Mbeki, pointed out in response: if only we had ever started doing so.

But the opponents of imperialism are by far the more numerous. Nearly two-thirds of the public believe British foreign policy is too subservient to the US and that the foreign occupations are a failure. The strength of the anti-war movement over the past five years, drawing fresh support during the Lebanon war, testifies that this sentiment goes much further than opinion polls.

Against this renewed left, there has coagulated a coalition of the brazen conservatives in Washington and their transatlantic admirers, including the two parliamentary frontbenches and a pseudo-social-democratic "new right" addicted to the spread of its values at the point of the imperial bayonet. They have set aside the left's traditional support for international law and the UN in favour of backing Bush's endless war.

We can now see where making "anti-anti-imperialism" your touchstone leads. The pro-war bloggers and lecturers who produced the Euston manifesto earlier this year have recently been reduced to providing a platform for Blairite ministers to promote privatisation, just as their stateside superhero Christopher Hitchens backed George Bush's re-election in 2004. They have resuscitated the gloomy traditions of the Fabian Colonial Bureau, whose doyenne Rita Hinden patronised Ghana's Kwame Nkrumah, when he came to London to rally support for his country's freedom, with the thought that "British socialists are not so concerned with ideals like independence and self-government".

But it is the tradition of the socialist pioneer William Morris which has come to dominate the left. Morris's support for the Mahdi's rebellion in the Sudan, on the grounds that he at least restored his country to its own people, is detailed in John Newsinger's new history of Britain's empire, The Blood Never Dried.

Empire is of course no longer something that simply happens "over there". Its fault lines run through every British community, with the wars in the Middle East and south Asia now accompanied by a campaign against the new "enemy within", the Muslim peoples of Britain.

One consequence of this has been a serious political engagement by the left with the Muslim communities, united in opposition to war and support of civil liberties. This is also a worldwide alliance. Seven Lebanese Communist fighters died resisting Israel's attack alongside Hizbullah, which has also had the support of the leaders of the Latin American left.

Fifty years on, the alliance of unequals forged between the US and Britain in the aftermath of Suez is once again unravelling in the Middle East.